A typical silencer, i.e. noise reducing muffler is one which has a central air flow corridor surrounded by a chamber packed with sound dampening material.
Although this known type of muffler is relatively efficient, attempts have been made to make it more efficient. For example, mufflers have been developed with baffles within the central air flow region surrounded by the packing material. These baffles, while effective from a sound diminishing standpoint, adversely affect the performance of the blower because of the back pressure that they provide against the air output from the blower.